In recent years, for the purpose of measures against problems such as sick building syndrome, solvent-free adhesives have been preferred as interior adhesives such as floor adhesives. Among them, an adhesive prepared with an organic polymer having a reactive silicon group or, in particular, a polyoxyalkylene-based polymer having a reactive silicon group has excellent workability and satisfactory curability, and therefore has been used as a solvent-free floor adhesive or, in particular, as a solvent-free wooden-floor adhesive.
However, in comparison with conventional solvent-based adhesives, the solvent-free adhesives have higher viscosity in general, thus causing a problem of deterioration in applicability, especially when used as floor adhesives to be applied to wide areas. In order to solve the problem, an ingenious attempt has been made to reduce viscosity with use of a filler having a large particle diameter. However, such an attempt causes an adhesive to drip when scooped up with a trowel, thus causing a problem of deterioration in workability.
It has been reported that an adhesive having thixotropic properties obtained by adding approximately 100 parts by weight of colloidal calcium carbonate to a polyoxyalkylene-based polymer having a reactive silicon group is effective as means to solve these problems (e.g., see Patent Documents 1 and 2). However, unfortunately, these adhesives are not only insufficient in applicability when applied to wide areas, but also too expensive for such applications.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 105956/2003 (Tokukai 2003-105956)    Patent Document 2: Japanese Unexamined Patent Application Publication No. 171217/2005 (Tokukai 2005-171217)